A multidisk oil-bath clutch comprises a cylindrical housing that houses a number of drive disks alternating with a corresponding number of driven disks; the lateral surfaces of the drive disks are covered on both sides with friction material, while the lateral surfaces of the driven disks are smooth; or only one side of the lateral surface of both the drive and driven disks is covered with friction material. In an externally driven clutch, the drive disks are angularly integral with the cylindrical housing, while the driven disks are integral with a central hub extending outwards of the cylindrical housing on one side; and vice versa in the case of an internally driven clutch, i.e., the driven disks are angularly integral with the cylindrical housing, and the drive disk are integral with the central hub.
Pressurized oil is fed constantly into the housing, and substantially serves to cool the disks and lubricate the rotating parts. The oil is normally fed axially through at least one inlet opening at a first end of the disk pack, and is extracted axially through at least one outlet opening at a second end, opposite the first end, of the disk pack.
The performance of a multidisk oil-bath clutch—i.e., the maximum torque that can be transmitted, and the ability to operate with slippage between the drive and driven disks (to adapt speed) for a prolonged period of time—depends on the maximum amount of overheating to which the disks are subjected (over and above a given temperature, the friction material deteriorates, and the disk metal may undergo deformation). To improve performance of a multidisk oil-bath clutch, the amount of heat generated is reduced and/or the cooling is improved. To reduce the amount of heat generated, for a given friction material, the contact surface area between the drive and driven disks (i.e., the number and/or size of the disks) is increased. This solution, however, may result in an increase in the size (axial and/or radial) and weight of the clutch. To improve cooling, it has been proposed to increase oil flow to the clutch. This, however, calls for a larger (and therefore heavier) oil supply circuit, which may still pose serious limitations in that, for a given circuit size, an increase in oil flow to the clutch may mean a corresponding increase in oil feed pressure.
International Patent Application Publication No. WO 2004/013508, which is incorporated herein by reference, describes a multidisk oil-bath clutch comprising: a housing mounted for rotation about a longitudinal axis of rotation; a hub mounted for rotation about the longitudinal axis of rotation and housed inside and coaxially with the housing; a number of drive disks housed inside the housing and angularly integral with the housing or hub; a number of driven disks housed inside the housing, alternating with the drive disks, and angularly integral with the hub or housing; at least one oil inlet into the housing; and at least one oil outlet from the housing. Each drive disk has a number of first circulation channels equally spaced about the longitudinal axis of rotation and extending radially from an inner edge of the drive disk to an outer edge of the drive disk; and each driven disk has a number of second circulation channels equally spaced about the longitudinal axis of rotation and extending radially from an inner edge of the driven disk to an outer edge of the driven disk.